There are two themes in this proposed P01: (1) to develop effective population-based behavioral interventions for dietary change and smoking cessation; and 2) to develop methodology for evaluating population-based interventions. These themes evolved out of our past experience in cancer prevention studies, and address the effort to move from efficacy studies in volunteers to trials of generalizable effectiveness. The P01 includes four projects that address: methodology for evaluation of community-based cancer control studies (Project 1); the relative effectiveness of two delivery methods for worksite-wide smoking cessation programs (Project 2); self-help dietary intervention for decreasing fat and increasing fruit and vegetable consumption (Project 3); and intervention processes and dose- response effects in worksite smoking cessation and dietary change programs (Project 4). The P01 also includes a leadership core, a shared resource core, and a developmental research core. The leadership core provides stable leadership and collaborative institutional and community relationships. The shared resource core provides data collection and database management services, as well as procedures for cost and cost- effectiveness. The developmental research core includes two exploratory studies that address: community organization of a substantial minority group in Washington State (DRI 1); and validity of three approaches to assess nutritional supplement use (DRI 2). The investigators have worked closely together as a research team for more than five years. Costs and cost effectiveness of the proposed interventions, including all pertinent aspects of community-wide change, add an important feature to the P01. The research also focuses on the inclusion of minority and hard to reach groups in population-based research.